Manufacturing method of monomer composition for synthesizing recycled plastics, manufacturing apparatus for monomer composition for synthesizing recycled plastics, and monomer composition for synthesizing recycled plastics, recycled plastics, and molded articles using the same

Abstract

The present invention relates to a method for producing a monomer composition for synthesizing recycled plastics, the method including the steps of depolymerizing a polycarbonate resin in the presence of an alcohol, monitoring a Raman spectrum of an aromatic diol compound or alcohol obtained from the depolymerization reaction in a reactor where the depolymerization reaction is carried out, and recovering the aromatic diol compound; an apparatus for producing a monomer composition for synthesizing recycled plastics; and a monomer composition for synthesizing recycled plastics, recycled plastics, and molded articles using the same.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0109847, filed on August 22, 2023, and all contents disclosed in the documents of said Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a method and apparatus for producing a monomer composition for synthesizing recycled plastics, which improves efficiency by optimizing reaction conditions through real-time monitoring of the process of recycling aromatic diol compounds through chemical decomposition of polycarbonate resins, and to a monomer composition for synthesizing recycled plastics, recycled plastics, and molded articles using the same. [Background technology]

[0003] Polycarbonate is a thermoplastic polymer, a plastic with excellent properties such as excellent transparency, ductility, and relatively low manufacturing costs.

[0004] Polycarbonate is widely used for a variety of purposes, but concerns about the environmental and health impacts of its disposal have been raised.

[0005] Currently, physical recycling methods are being used, but this has led to problems with quality degradation, and research is underway into chemical recycling of polycarbonate.

[0006] Chemical decomposition of polycarbonate refers to the process of decomposing polycarbonate to obtain a monomer, an aromatic diol compound (e.g., bisphenol A (BPA)), which is then used again in polymerization to obtain high-purity polycarbonate.

[0007] Typical examples of such chemical decomposition include pyrolysis, hydrolysis, and alcoholysis. Among these, alcoholysis using a base catalyst is the most common method. However, methanolysis has the drawback of using methanol, which is harmful to the human body, and ethanol requires high temperature and pressure conditions, resulting in a low yield.

[0008] In addition, an alcohol decomposition method using an organic catalyst is known, but currently, this method has economic disadvantages.

[0009] On the other hand, as the reaction scale of polycarbonate decomposition reactions increases to several tens of liters, the need to explore the factors that cause differences in the depolymerization tendency at laboratory levels has emerged.

[0010] Conventionally, the conversion rate to the final product was analyzed by HPLC or NMR analysis, or samples were taken during the reaction and analyzed.

[0011] However, as the reaction scale increased, there was a difference in the polycarbonate conversion rate compared to the reaction carried out at the laboratory level, and there was also a difference in the timing and extent of the formation of by-products. Summary of the Invention [Problem to be solved by the invention]

[0012] The present invention provides a method and an apparatus for producing a monomer composition for synthesizing recycled plastics, which improves efficiency by optimizing reaction conditions through real-time monitoring of the process of recycling aromatic diol compounds through chemical decomposition of polycarbonate resins.

[0013] The present invention also provides a monomer composition for synthesizing recycled plastics, recycled plastics, and molded articles produced using the above-mentioned method for producing a monomer composition for synthesizing recycled plastics or the above-mentioned apparatus for producing a monomer composition for synthesizing recycled plastics. [Means for solving the problem]

[0014] In order to solve the above problems, the present specification provides a method for producing a monomer composition for synthesizing recycled plastics, the method including: depolymerizing a polycarbonate resin in the presence of an alcohol; monitoring a Raman spectrum of an aromatic diol compound or alcohol obtained from the depolymerization in a reactor where the depolymerization is performed; and recovering the aromatic diol compound.

[0015] The present specification also provides an apparatus for producing a monomer composition for synthesizing recycled plastics, the apparatus including: a reactor for depolymerizing a polycarbonate-based resin in the presence of an alcohol; an in-line analyzer inserted into the reactor for monitoring a Raman spectrum of an aromatic diol compound or alcohol obtained from the depolymerization; and a recovery section for recovering the aromatic diol compound obtained from the depolymerization.

[0016] The present specification also provides a monomer composition for synthesizing recycled plastics, which comprises an aromatic diol compound obtained by the method for producing a monomer composition for synthesizing recycled plastics or the apparatus for producing a monomer composition for synthesizing recycled plastics.

[0017] Also provided herein is a recycled plastic comprising the reaction product of the monomer composition for synthesizing recycled plastic and a comonomer.

[0018] Also provided herein is a molded article comprising the recycled plastic.

[0019] Hereinafter, a method for producing a monomer composition for synthesizing recycled plastics, an apparatus for producing a monomer composition for synthesizing recycled plastics, and a monomer composition for synthesizing recycled plastics, recycled plastics, and molded articles using the same according to specific embodiments of the invention will be described in more detail.

[0020] In this specification, unless expressly stated otherwise, terminology is for the purpose of referring to particular embodiments only and is not intended to limit the invention.

[0021] As used herein, the singular forms "a," "an," and "the" include the plural forms as well, unless the context clearly dictates to the contrary.

[0022] As used herein, "pH" refers to hydrogen ion concentration (pH), a numerical value that indicates the degree of acidity or alkalinity of a substance. It can be calculated by taking the reciprocal logarithm of the dissociated hydrogen ion concentration and is used as a measure of the acidity or base strength of a substance.

[0023] As used herein, the meaning of "comprising" embodies certain properties, regions, integers, steps, operations, elements, and / or components, and does not exclude the presence or addition of other certain properties, regions, integers, steps, operations, elements, components, and / or groups.

[0024] In this specification, terms including ordinal numbers such as "first" and "second" are used to distinguish one component from another, and are not limited by the ordinal numbers. For example, within the scope of the present invention, a first component may be referred to as a second component, and similarly, a second component may be referred to as a first component.

[0025] 1. Method for producing monomer composition for synthesizing recycled plastics According to one embodiment of the present invention, there is provided a method for producing a monomer composition for synthesizing recycled plastics, the method including: depolymerizing a polycarbonate-based resin in an alcohol; monitoring a Raman spectrum of an aromatic diol compound or alcohol obtained from the depolymerization in a reactor where the depolymerization is performed; and recovering the aromatic diol compound.

[0026] The present inventors have confirmed through experiments that, in the process of recycling polycarbonate-based resins by chemical decomposition, as in the method for producing a monomer composition for synthesizing recycled plastics according to the embodiment, it is possible to terminate the depolymerization reaction at an optimal point by monitoring the Raman spectrum of the aromatic diol compound or alcohol obtained from the depolymerization reaction in a reactor where the depolymerization reaction is performed, and to recover a high-purity aromatic diol compound in a high yield, thereby completing the invention.

[0027] In particular, conventional methods have been limited in that it is difficult to find an optimal reaction end point for obtaining a high-purity, high-yield aromatic diol compound as a target substance for recovery, by analyzing the conversion rate to the final product by HPLC or NMR analysis or by taking and analyzing a sample at any point during the reaction.

[0028] In contrast, in the present invention, in the process of recycling polycarbonate-based resins through chemical decomposition, an analyzer installed in a reactor where a depolymerization reaction is performed is used to obtain a Raman spectrum of the aromatic diol compound or alcohol obtained from the depolymerization reaction in real time while the depolymerization reaction is being carried out, and the Raman spectrum is analyzed to determine the approximate aromatic diol compound or alcohol, thereby enabling more accurate detection of the optimal reaction end point. Furthermore, by minimizing the generation of reaction by-products while monitoring the generation of reaction by-products in real time, it is possible to recover aromatic diol compounds with high purity and high yield.

[0029] Specifically, the method for preparing a monomer composition for synthesizing recycled plastics according to one embodiment may include depolymerizing a polycarbonate-based resin in the presence of alcohol.

[0030] The term "polycarbonate-based resin" refers to any homopolymer or copolymer containing a polycarbonate repeating unit, collectively referring to a reaction product obtained by the polymerization or copolymerization of a monomer containing an aromatic diol compound and a carbonate precursor. A homopolymer can be synthesized by using only one aromatic diol compound and one carbonate precursor to obtain a single carbonate repeating unit. Alternatively, a copolymer can be synthesized by using one aromatic diol compound and two or more carbonate precursors, two or more aromatic diol compounds and one carbonate precursor, or one aromatic diol compound and one carbonate precursor plus one or more other diols to obtain two or more carbonates. The homopolymer or copolymer can include low molecular weight compounds, oligomers, and polymers within a range of molecular weights.

[0031] The polycarbonate-based resin may be applied regardless of various forms and types, such as a new polycarbonate-based resin produced by synthesis, a recycled polycarbonate-based resin produced by a recycling process, or a polycarbonate-based resin waste.

[0032] However, if necessary, a pretreatment process for the polycarbonate resin may be performed before the depolymerization reaction of the polycarbonate resin to increase the efficiency of the process for recovering the aromatic diol compound and the carbonate precursor from the polycarbonate resin. Examples of the pretreatment process include washing, drying, pulverization, and glycol decomposition. The specific method for each pretreatment process is not limited, and various methods widely used in the process for recovering the aromatic diol compound and the carbonate precursor by depolymerization of the polycarbonate resin may be applied without limitation.

[0033] The depolymerization reaction of the polycarbonate-based resin may be carried out under acidic, neutral, or basic conditions, and particularly under basic (alkaline) conditions. The type of base is not particularly limited, and examples include sodium hydroxide (NaOH) or potassium hydroxide (KOH). The base is a basic catalyst that acts as a catalyst and has the advantage of being more economical than organic catalysts that are mainly used under mild conditions. More specifically, the depolymerization reaction of the polycarbonate-based resin may be carried out at a pH in the range of more than 8 and less than 12.

[0034] The depolymerization of the polycarbonate resin can be carried out by reacting the base in an amount of 0.5 moles or less, or 0.4 moles or less, or 0.3 moles or less, or 0.1 moles or more, or 0.2 moles or more, or 0.1 to 0.5 moles, or 0.1 to 0.4 moles, or 0.1 to 0.3 moles, or 0.2 to 0.5 moles, or 0.2 to 0.4 moles, or 0.2 to 0.3 moles, per mole of the polycarbonate resin. If the base is reacted in an amount exceeding 0.5 moles per mole of the polycarbonate resin, the increased amount of alkali salt generated increases impurities, reducing the purity of the target recovered material and reducing the economic viability of the catalytic reaction.

[0035] The depolymerization reaction of the polycarbonate resin may be carried out in the presence of alcohol. The present invention has the advantage that the polycarbonate resin can be decomposed into alcohol to stably obtain a highly pure monomer, bisphenol A, and that a carbonate compound, such as a dialkyl carbonate, with high added value can be additionally obtained as a reaction by-product.

[0036] The number of hydroxy groups in the alcohol is not particularly limited, but may include, for example, a monohydric alcohol, which is a compound having one hydroxy group in the molecule.

[0037] Furthermore, the type of monovalent organic functional group bonded to the hydroxy group in the monohydric alcohol is not particularly limited, but may include organic functional groups having 1 to 10 or 1 to 6 carbon atoms, such as alkyl groups, cycloalkyl groups, aryl groups, heteroaryl groups, or combinations of two or more of these.

[0038] The alcohol may be one type of single compound or a mixture of two or more types. Specific examples of the alcohol are not particularly limited, but include ethanol, methanol, phenol, and mixtures thereof.

[0039] The content of the alcohol may be 5 to 15 mol or 8 to 13 mol per mol of the polycarbonate-based resin. Since the alcohol has good solubility in bisphenol A, an alcohol within the above range must be included. If the content of the alcohol is too low, less than 5 mol per mol of the polycarbonate-based resin, the alcoholysis of the polycarbonate-based resin is difficult to carry out sufficiently. On the other hand, if the content of the alcohol is too high, more than 15 mol per mol of the polycarbonate-based resin, excessive use of alcohol may reduce the economic efficiency of the process.

[0040] The solvent in which the depolymerization reaction of the polycarbonate-based resin is carried out may include one or more organic solvents selected from the group consisting of tetrahydrofuran, toluene, methylene chloride, chloroform, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and dipropyl carbonate.

[0041] The organic solvent may include tetrahydrofuran, toluene, methylene chloride, chloroform, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, dipropyl carbonate, or a mixture of two or more thereof.

[0042] More preferably, methylene chloride can be used as the organic solvent. When methylene chloride is used as the organic solvent, there is an advantage that the dissolving property for polycarbonate is improved, thereby improving the reactivity.

[0043] The content of the organic solvent may be 16 to 20 moles or 16 to 18 moles per mole of the polycarbonate resin. The content of the organic solvent may be 1.5 to 2 moles per mole of the alcohol. By mixing the polycarbonate resin, alcohol, and organic solvent within the above ranges, a desired level of depolymerization reaction of the polymer can be achieved.

[0044] Meanwhile, the temperature at which the depolymerization reaction of the polycarbonate resin proceeds is not particularly limited, but may be, for example, 20° C. to 100° C. or 50° C. to 70° C. The time for which the depolymerization reaction of the polycarbonate resin proceeds may be 1 hour to 30 hours or 4 hours to 6 hours.

[0045] Specifically, the above conditions are milder process conditions than the existing pressurized / high temperature process, and stirring under these conditions allows the process to be carried out in a milder process than the existing pressurized / high temperature process. In particular, stirring at 50°C to 70°C for 4 to 6 hours has the advantage of providing the most efficient results in terms of reproducibility and certifiability.

[0046] In other words, the present invention has the advantage that a high-purity aromatic diol compound (e.g., bisphenol A) can be obtained under mild conditions without using an organic catalyst, by adjusting the type and amount of the mixed solvent and the type and content of the base catalyst, and without using a pressurized / high-temperature process, and that diethyl carbonate can be obtained as a by-product because ethanol is used.

[0047] Meanwhile, an antioxidant can be added to the reaction solution during the depolymerization of the polycarbonate-based resin. By adding the antioxidant, the aromatic diol compound recovered by recycling the polycarbonate-based resin through chemical decomposition can satisfy a low color coordinate b* value at a color level equivalent to that of commercially available reagents or reagents used for PC polymerization.

[0048] Specific examples of the antioxidant are not particularly limited, and various antioxidants that have been widely used in conventional technical fields can be used without limitation, including, for example, sodium hyposulfite, sodium sulfite, erythorbic acid, dibutylhydroxytoluene, butylhydroxyanisole, α-tocopherol, tocopherol acetate, L-ascorbic acid and its salts, L-ascorbic acid palmitate, L-ascorbic acid stearate, triamyl gallate, propyl gallate, disodium ethylenediaminetetraacetate (EDTA), sodium pyrophosphate, sodium metaphosphate, or a mixture of two or more thereof.

[0049] The specific amount of the antioxidant to be added is not particularly limited, but for example, it may be added in a range of 0.1 wt % to 5 wt % or 0.1 wt % to 1 wt % based on the weight of the total reaction solution, at a level that does not affect the physical properties of the monomer composition for synthesizing recycled plastics.

[0050] In addition, during the depolymerization reaction of the polycarbonate-based resin, the depolymerization reaction may be performed under a nitrogen atmosphere.

[0051] More specifically, the step of depolymerizing the polycarbonate-based resin may include a first step of dissolving the carbonate-based resin in an organic solvent, and a second step of adding and stirring a catalyst solution containing an alcohol, a base, and an antioxidant. The alcohol, organic solvent, base, antioxidant, and polycarbonate-based resin in the first and second steps are the same as those described above.

[0052] Meanwhile, the method for producing a monomer composition for synthesizing recycled plastics according to one embodiment may include monitoring a Raman spectrum of the aromatic diol compound or alcohol obtained from the depolymerization reaction in a reactor where the depolymerization reaction is performed. The Raman spectrum of the aromatic diol compound or alcohol obtained from the depolymerization reaction can be monitored in real time during the depolymerization reaction using an analyzer installed in the reactor where the depolymerization reaction is performed, thereby enabling more accurate detection of an optimal reaction end point. Additionally, by monitoring the generation of reaction by-products in real time and minimizing the generation of by-products, a high-purity aromatic diol compound can be recovered in high yield.

[0053] In the step of monitoring the Raman spectrum of the aromatic diol compound or alcohol obtained from the depolymerization reaction in the reactor where the depolymerization reaction is performed, the Raman spectrum is data obtained by Raman analysis. The Raman analysis may be performed using any of a variety of conventionally known analytical methods, analytical devices, and analytical conditions. For example, an all-in-one device from MarqMetrix may be used.

[0054] In particular, the step of monitoring the Raman spectrum of the aromatic diol compound or alcohol obtained from the depolymerization reaction in the reactor where the depolymerization reaction is performed may be performed using a Raman spectrometer inserted into the reactor. More specifically, in the embodiment, real-time changes in chemical components in the solid / liquid reaction solution may be analyzed in a non-destructive manner using an in-line probe, which is a Raman spectrometer inserted into the reactor.

[0055] As a result, by using an in-line Raman analyzer to check in real time the Raman spectra of aromatic diol compounds (e.g., bisphenol A) produced by the depolymerization reaction of polycarbonate resin, or the alcohols (e.g., ethanol) participating in the reaction, it became possible to indirectly predict how the concentration and content of aromatic diol compounds (or alcohols) would change in real time. More specifically, a PLS (partial least squares) prediction model could be established by correlating Raman spectrum data with the concentration and content values ​​obtained by HPLC analysis.

[0056] The Raman spectrometer can be manufactured to withstand the reaction pressure and inserted into a reactor where the depolymerization reaction is performed to collect reaction information in real time. One end of the Raman spectrometer can contact the depolymerization reactants, and the other end is connected to a computer to calculate and analyze the obtained Raman spectrum in real time. Specific details regarding the Raman spectrometer can be those known in the art without limitation. However, for example, a ball probe can be used.

[0057] For example, the step of monitoring the Raman spectrum may include measuring an integral ratio of the aromatic diol compound or alcohol obtained from the depolymerization reaction in a reactor where the depolymerization reaction is performed, according to the following Equation 1:

[0058] [Formula 1] Integral ratio of aromatic diol compounds = {791.2 cm on the Raman spectrum -1 ~861.5cm -1 The integral value of the region / (663.4 cm on the Raman spectrum) -1 ~785.1cm -1 + 234.8 cm on the Raman spectrum -1 ~337.1cm -1 (Integral value of the domain) In the above formula 1, 791.2 cm -1 ~861.5cm -1 The region of the spectrum is due to aromatic diol compounds, and the region of the spectrum is at 663.4 cm -1 ~785.1cm -1 , and 234.8 cm -1 ~337.1cm -1 The region is the spectrum due to the reaction solvent.

[0059] In Equation 1, since the methylene chloride component used as the depolymerization reaction solvent does not participate in the depolymerization reaction, the relative integral value was calculated by taking the integral value of the Raman band of the reaction solvent as the standard value and placing it in the denominator, and then taking the integral value of the Raman band of the aromatic diol compound as the numerator.

[0060] The integral ratio of the aromatic diol compound according to Equation 1 has a value between 0 and 0.15, and starts from 0 to 0.06 at the initial stage of the depolymerization reaction, rapidly increases to 0.1 or more or to 0.1 to 0.11 within 30 minutes after the start of the reaction, and after 30 minutes, tends to converge to a value between 0.11 to 0.15, 0.11 to 0.13, 0.110 to 0.125, 0.115 to 0.125, 0.115 to 0.122, or 0.12 to 0.122.

[0061] Based on this understanding of the trend, it was confirmed that when the integral ratio of the aromatic diol compound according to Formula 1 is 0.115 to 0.125, 0.115 to 0.122, or 0.12 to 0.122, the depolymerization reaction can be terminated, ensuring process efficiency and recovering a high-purity, high-yield aromatic diol compound. When the integral ratio of the aromatic diol compound according to Formula 1 is less than 0.115, it is difficult to ensure a sufficient yield of the aromatic diol compound. In contrast, when the integral ratio of the aromatic diol compound according to Formula 1 is greater than 0.125, it is difficult to ensure a sufficient purity of the aromatic diol compound as impurities other than the aromatic diol compound (e.g., impurities derived from the aromatic diol compound) increase, and the reaction proceeds too long, resulting in a decrease in process efficiency.

[0062] Meanwhile, the step of monitoring the Raman spectrum of the aromatic diol compound or alcohol obtained from the depolymerization reaction in the reactor where the depolymerization reaction is performed may be performed repeatedly at intervals of 5 minutes or less. Specifically, the step of monitoring the Raman spectrum of the aromatic diol compound or alcohol obtained from the depolymerization reaction in the reactor where the depolymerization reaction is performed may be performed repeatedly at intervals of 5 minutes or less, 4 minutes or less, or 3 minutes or less during the depolymerization reaction. The shorter the interval at which the Raman spectrum of the aromatic diol compound or alcohol obtained from the depolymerization reaction is monitored, the more accurately the optimal reaction end point can be determined and the generation of reaction by-products can be minimized.

[0063] In addition, as another specific example of monitoring the Raman spectrum, the step of monitoring the Raman spectrum of the aromatic diol compound or alcohol obtained from the depolymerization reaction in the reactor where the depolymerization reaction is performed may include measuring an integral ratio of alcohol according to the following Equation 2:

[0064] [Formula 2] Integral ratio of alcohol = {849.7 cm on the Raman spectrum -1 ~910cm -1 The integral value of the region / (663.4 cm on the Raman spectrum) -1 ~785.1cm -1 + 234.8 cm on the Raman spectrum -1 ~337.1cm -1 (Integral value of the domain) In the above formula 2, 849.7 cm -1 ~910cm -1 The region of the spectrum is due to alcohol, and the region of the spectrum is 663.4 cm -1 ~785.1cm -1 , and 234.8 cm -1 ~337.1cm -1 The region is the spectrum due to the reaction solvent.

[0065] In Equation 2, the methylene chloride component used as the depolymerization solvent does not participate in the depolymerization reaction. Therefore, the relative integral value was calculated by taking the integral value of the Raman band of the reaction solvent as the standard value and placing it in the denominator, and then taking the integral value of the Raman band of the alcohol as the numerator.

[0066] The integral ratio of alcohol according to Equation 2 has a value between 0 and 1.1, and starts from 0.15 or more or 0.15 to 1.1 at the beginning of the depolymerization reaction, rapidly decreases to 0.11 or less or 0.1 to 0.11 within 30 minutes after the start of the reaction, and tends to converge to a value between 0.09 to 0.1 or 0.095 to 0.1 after 30 minutes.

[0067] Based on this understanding of the trend, it was confirmed that when the integral ratio of the alcohol according to Equation 2 is 0.09 to 0.1 or 0.095 to 0.1, the depolymerization reaction can be terminated, ensuring process efficiency while recovering a high-purity, high-yield aromatic diol compound. When the integral ratio of the alcohol according to Equation 2 exceeds 0.1, it becomes difficult to ensure a sufficient yield of the aromatic diol compound. In contrast, when the integral ratio of the alcohol according to Equation 2 decreases to less than 0.09, impurities other than the aromatic diol compound (e.g., impurities derived from the aromatic diol compound) increase, making it difficult to ensure a sufficient purity of the aromatic diol compound, and the reaction proceeds for an excessively long time, resulting in a decrease in process efficiency.

[0068] Furthermore, the step of monitoring the Raman spectrum of the aromatic diol compound or alcohol obtained from the depolymerization reaction in the reactor where the depolymerization reaction is performed may be performed repeatedly at intervals of 5 minutes or less. Specifically, the step of monitoring the Raman spectrum of the aromatic diol compound or alcohol obtained from the depolymerization reaction in the reactor where the depolymerization reaction is performed may be performed repeatedly at intervals of 5 minutes or less, 4 minutes or less, or 3 minutes or less during the depolymerization reaction. The shorter the interval at which the Raman spectrum of the aromatic diol compound or alcohol obtained from the depolymerization reaction is monitored, the more accurately the optimal reaction end point can be determined and the generation of reaction by-products can be minimized.

[0069] Meanwhile, the step of monitoring a Raman spectrum of the aromatic diol compound or alcohol obtained from the depolymerization reaction in a reactor where the depolymerization reaction is performed may further include the step of monitoring a Raman spectrum of impurities derived from the aromatic diol compound produced in the depolymerization reaction.

[0070] The impurities derived from the aromatic diol compound are by-products generated as the depolymerization reaction proceeds excessively, and they reduce the purity of the aromatic diol compound to be recovered, bisphenol A. Therefore, by monitoring the Raman spectrum of the impurities derived from the aromatic diol compound generated in the depolymerization reaction in real time, the presence or absence of reaction by-products can be monitored in real time, and the by-products can be minimized, thereby enabling the recovery of a high-purity, high-yield aromatic diol compound.

[0071] The impurities derived from aromatic diol compounds refer to all substances excluding aromatic diol compounds, which are the main target substances for recovery in the present invention, and the specific types thereof are not particularly limited, but examples thereof include p-tert-butylphenol.

[0072] Specifically, the step of monitoring the Raman spectrum of the impurities derived from the aromatic diol compound generated in the depolymerization reaction may include measuring the integral ratio of the impurities derived from the aromatic diol compound according to Equation 3 below.

[0073] [Formula 3] Integral ratio of impurities derived from aromatic diol compounds = {800 cm on the Raman spectrum -1 ~850cm -1 The integral value of the region / (663.4 cm on the Raman spectrum) -1 ~785.1cm -1 + 234.8 cm on the Raman spectrum -1 ~337.1cm -1 (Integral value of the domain) In the above formula 3, 800 cm on the Raman spectrum -1 ~850cm -1 The region of the spectrum is due to impurities derived from aromatic diol compounds, and the region of the spectrum of 663.4 cm -1 ~785.1cm -1 , and 234.8 cm -1 ~337.1cm -1The region is the spectrum due to the reaction solvent.

[0074] In Equation 3, since the methylene chloride component used as the depolymerization reaction solvent does not participate in the depolymerization reaction, the relative integral value was calculated by taking the integral value of the Raman band of the reaction solvent as the standard value and placing it in the denominator, and then taking the integral value of the Raman band of the impurity derived from the aromatic diol compound as the numerator.

[0075] When the integral ratio of the impurities derived from the aromatic diol compound according to Equation 3 exceeds 0.12, the depolymerization reaction can be terminated, ensuring process efficiency while recovering a high-purity, high-yield aromatic diol compound. When the integral ratio of the impurities derived from the aromatic diol compound according to Equation 3 exceeds 0.12, impurities other than the aromatic diol compound (e.g., impurities derived from the aromatic diol compound) increase, making it difficult to sufficiently ensure the purity of the aromatic diol compound, and the reaction proceeds for an excessively long time, reducing process efficiency.

[0076] Meanwhile, the method for producing a monomer composition for synthesizing recycled plastics according to one embodiment may include recovering the aromatic diol compound obtained from the depolymerization reaction. Specific examples of the aromatic diol compound include bis(4-hydroxyphenyl)methane, bis(4-hydroxyphenyl)ether, bis(4-hydroxyphenyl)sulfone, bis(4-hydroxyphenyl)sulfoxide, bis(4-hydroxyphenyl)sulfide, bis(4-hydroxyphenyl)ketone, 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), 2,2-bis(4-hydroxyphenyl)butane, and 1,1-bis(4-hydroxyphenyl)cyclohexane (bis Examples of the aromatic diol compound include 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, 2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane, 2,2-bis(4-hydroxy-3-bromophenyl)propane, 2,2-bis(4-hydroxy-3-chlorophenyl)propane, 2,2-bis(4-hydroxy-3-methylphenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, and mixtures of two or more thereof. Preferably, the aromatic diol compound in the monomer composition for synthesizing recycled plastics according to the embodiment may be 2,2-bis(4-hydroxyphenyl)propane (bisphenol A).

[0077] Specifically, the step of recovering the aromatic diol compound obtained from the depolymerization reaction may include a step of adding an acid so that the pH of the depolymerization reaction product is 2 to 8. The acid may be a strong acid, for example, hydrochloric acid (HCl).

[0078] The salt of the aromatic diol compound contained in the depolymerization reaction product can be converted to the aromatic diol compound by adding an acid so that the pH of the depolymerization reaction product is 2 to 8. The depolymerization reaction is carried out under basic conditions, and the aromatic diol compound produced exists in the form of a salt through a reaction with the base, and is hydrophilic. Therefore, by adding an acid, the salt of the aromatic diol compound contained in the depolymerization reaction product can be converted to the aromatic diol compound, thereby making the depolymerization reaction product hydrophobic.

[0079] Therefore, in the step of removing impurities by adding water after adding the acid (described later), a water layer containing impurities and an organic solvent layer containing the aromatic diol compound and the carbonate precursor can be formed. Because the aromatic diol compound and the carbonate precursor are hydrophobic, they may be contained in the organic solvent layer between water and the organic solvent, or various water-soluble impurities may be contained in the water layer. As a result, the aromatic diol compound, which is the main product, and the impurities can be easily separated even with just the simple process of changing the pH.

[0080] The step of adding an acid to adjust the pH of the depolymerization reaction product to 2 to 8 may further include a step of adding water, which may result in the formation of separate layers, i.e., an aqueous layer containing impurities and an organic solvent layer containing the aromatic diol compound and the carbonate precursor, in the impurity removal step described below.

[0081] The order of the acid addition step and the water addition step is not particularly limited, and it is possible to add water after acid addition, or add water after acid addition, or add water and acid simultaneously.

[0082] Meanwhile, the step of recovering the aromatic diol compound obtained from the depolymerization reaction may include the step of removing impurities after the addition of the acid, whereby the impurities may include hydrophilic substances such as salt compounds, ionic compounds, and acid compounds.

[0083] As described above, after the step of adding an acid to adjust the pH of the depolymerization reaction product to 2 to 8, the step of removing impurities from the depolymerization reaction product after the acid addition is carried out. This allows the depolymerization reaction product to form a layer separated into an aqueous layer containing impurities and an organic solvent layer containing an aromatic diol compound and a carbonate precursor, from which the aqueous layer containing impurities can be separated and removed.

[0084] In the step of removing impurities from the depolymerization reaction product after the addition of the acid, the aqueous layer may be separated from the organic layer, and the impurities contained in the aqueous layer may be removed. Specific separation conditions for separating the aqueous layer from the organic layer are not particularly limited, and various known purification techniques may be applied to specific separation devices and methods without limitation. However, for example, a drain device may be used.

[0085] Meanwhile, the step of recovering the aromatic diol compound obtained from the depolymerization reaction may include separating a carbonate precursor from the depolymerization reaction product, and thus, the separated carbonate precursor may include diethyl carbonate.

[0086] The step of separating the carbonate precursor from the depolymerization reaction product may include a step of vacuum distillation of the depolymerization reaction product. Although examples of the vacuum distillation conditions are not particularly limited, in one specific example, the polycarbonate-based resin may be subjected to low-temperature distillation by pressurizing the depolymerization reaction product at a pressure of 200 mbar to 300 mbar and a temperature of 20°C to 30°C, followed by reducing the pressure to 10 mbar to 50 mbar and a temperature of 20°C to 30°C.

[0087] The separated carbonate precursor can be reused without a separate separation and purification process, or can be reused after, if necessary, conventional separation and purification processes such as extraction, adsorption, drying, etc. Specific purification conditions are not particularly limited, and various known purification techniques can be applied without limitation to specific purification devices and methods.

[0088] Meanwhile, the step of recovering the aromatic diol compound obtained from the depolymerization reaction may further include a step of purifying the depolymerization reaction product from which the carbonate precursor has been separated, after the step of separating the carbonate precursor from the depolymerization reaction product.

[0089] Specifically, the step of purifying the depolymerization reaction product from which the carbonate precursor has been separated may include a step of washing the depolymerization reaction product from which the carbonate precursor has been separated. Further, the step of purifying the depolymerization reaction product from which the carbonate precursor has been separated may include a step of adsorption purification of the depolymerization reaction product from which the carbonate precursor has been separated. Furthermore, the step of purifying the depolymerization reaction product from which the carbonate precursor has been separated may include a step of recrystallization of the depolymerization reaction product from which the carbonate precursor has been separated.

[0090] The order of the washing step, the adsorption purification step, and the recrystallization step is not particularly limited and may be any order. For example, the washing step, the adsorption purification step, and the recrystallization step may be performed in this order. The washing step, the adsorption purification step, and the recrystallization step may each be repeated at least once. Specific washing, adsorption, and recrystallization apparatuses and methods may be selected from various known purification techniques without limitation.

[0091] In the step of washing the depolymerization reaction product from which the carbonate precursor is separated, the depolymerization reaction product from which the carbonate precursor is separated may contain an aromatic diol compound. However, since various impurities remain during the recovery process of obtaining the aromatic diol compound, washing may be performed to sufficiently remove the impurities to obtain a high-purity aromatic diol compound.

[0092] Specifically, the cleaning step may include cleaning with a solvent at a temperature of 10° C. to 30° C. or 20° C. to 30° C. The temperature condition refers to the temperature inside a cleaning vessel where cleaning with a solvent is performed, and various heating devices may be used without limitation to maintain a high temperature above room temperature.

[0093] The solvent used in the washing step may include one of water, alcohol, and organic solvents, such as tetrahydrofuran, toluene, methylene chloride, chloroform, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, dipropyl carbonate, or a mixture of two or more thereof.

[0094] The solvent used in the washing step may be used in a weight ratio of 1 to 30 parts by weight, or 1 to 10 parts by weight, based on 1 part by weight of the polycarbonate-based resin used in the depolymerization reaction.

[0095] More specifically, the solvent used in the step of washing with a solvent at a temperature of 10°C to 30°C may be an organic solvent. Preferably, methylene chloride can be used as the organic solvent. In this case, the organic solvent can be used in an amount of 1 part by weight to 10 parts by weight per 1 part by weight of the polycarbonate resin.

[0096] In addition, the step of adsorbing and purifying the depolymerization reaction product from which the carbonate precursor has been separated may include the step of adding an adsorbent to the depolymerization reaction product from which the carbonate precursor has been separated, performing adsorption purification, and then removing the adsorbent. In the step of adding an adsorbent to the depolymerization reaction product from which the carbonate precursor has been separated, performing adsorption purification, and then removing the adsorbent, the adsorbent may be contacted with the depolymerization reaction product.

[0097] Examples of the adsorbent include activated carbon, charcoal, or a mixture thereof. Activated carbon is a black carbon material with micropores produced by subjecting raw materials to a carbonization process at about 500°C and an activated carbon process at about 900°C. Examples of the adsorbent are not particularly limited, and various activated carbons, such as plant-based, coal-based, petroleum-based, and waste-based activated carbons, can be used without limitation depending on the type of raw material.

[0098] More specific examples of plant-based activated carbon include coconut activated carbon, wood activated carbon, and sawdust activated carbon. Furthermore, coal-based activated carbon includes lignite activated carbon, bituminous activated carbon, and anthracite activated carbon. Furthermore, petroleum-based activated carbon includes petroleum coke activated carbon and oil carbon activated carbon. Furthermore, waste-based activated carbon includes synthetic resin activated carbon and pulp activated carbon.

[0099] The adsorbent may include one or more activated carbons selected from the group consisting of plant-based activated carbon, coal-based activated carbon, petroleum-based activated carbon, and waste-based activated carbon, i.e., the adsorbent may include plant-based activated carbon, coal-based activated carbon, petroleum-based activated carbon, waste-based activated carbon, or a mixture of two or more thereof.

[0100] More specifically, the adsorbent may include one or more activated carbons selected from the group consisting of palm activated carbon, lignite activated carbon, anthracite activated carbon, and bituminous activated carbon, i.e., palm activated carbon, lignite activated carbon, anthracite activated carbon, bituminous activated carbon, or a mixture of two or more thereof.

[0101] The adsorption purification conditions using the adsorbent are not particularly limited, and various conventional adsorption purification conditions can be used without limitation. However, for example, the amount of adsorbent added may be 40% to 60% by weight relative to the polycarbonate resin, the adsorption time may be 1 to 5 hours, and the adsorption method may be stirring adsorption or a laboratory adsorption tower.

[0102] If necessary, the method may further include adding a solvent to the depolymerization reaction product from which the carbonate precursor has been separated, before the step of adding an adsorbent to the depolymerization reaction product from which the carbonate precursor has been separated and then removing the adsorbent. An example of the solvent is ethanol, which may be added in a ratio of 1 to 20 moles, 10 to 20 moles, or 15 to 20 moles per mole of the polycarbonate resin. By adding a solvent to the depolymerization reaction product from which the carbonate precursor has been separated, the aromatic diol compound crystals contained in the depolymerization reaction product from which the carbonate precursor has been separated can be redissolved in the solvent.

[0103] Meanwhile, in the recrystallization step of the depolymerization reaction product from which the carbonate precursor is separated, various impurities contained in the depolymerization reaction product from which the carbonate precursor is separated can be sufficiently removed, thereby obtaining a high-purity aromatic diol compound.

[0104] Specifically, the recrystallization step may include adding water to the depolymerization reaction product from which the carbonate precursor has been separated to recrystallize the product. By adding water to the depolymerization reaction product from which the carbonate precursor has been separated to recrystallize the product, the solubility of the aromatic diol compound or a salt thereof contained in the depolymerization reaction product is increased, allowing impurities sandwiched between the crystals or between the crystals to be dissolved to the maximum extent in the solvent. Since the dissolved aromatic diol compound has poorer solubility than the impurities, the aromatic diol compound can easily precipitate as crystals when the temperature is subsequently lowered due to the difference in solubility.

[0105] More specifically, in the step of adding water to the depolymerization reaction product from which the carbonate precursor has been separated to recrystallize it, 200 to 400 moles or 250 to 350 moles of water can be used per mole of polycarbonate resin. If too little water is used, the temperature required to dissolve the aromatic diol compound contained in the depolymerization reaction product from which the carbonate precursor has been separated becomes too high, resulting in poor process efficiency and making it difficult to remove impurities through recrystallization. On the other hand, if too much water is used, the solubility of the aromatic diol compound contained in the depolymerization reaction product from which the carbonate precursor has been separated becomes too high, resulting in a reduced yield of the aromatic diol compound recovered after recrystallization, and the use of a large amount of solvent can reduce process efficiency.

[0106] If necessary, after the recrystallization step of the depolymerization reaction product from which the carbonate precursor has been separated, a step of removing remaining impurities by filtration or adsorption may be additionally performed.

[0107] Furthermore, if necessary, a drying step may be further included after the recrystallization step. The residual solvent can be removed by the drying, and the specific drying conditions are not particularly limited, but the drying can be performed at a temperature of, for example, 10°C to 100°C, or 10°C to 50°C. Regarding the specific drying apparatus and method used in the drying, various known drying techniques can be applied without any restrictions.

[0108] 2. Monomer manufacturing equipment for synthesizing recycled plastics According to another embodiment of the present invention, there is provided an apparatus for producing a monomer composition for synthesizing recycled plastics, the apparatus including: a reactor for depolymerizing a polycarbonate-based resin in the presence of an alcohol; an in-line analyzer inserted into the reactor for monitoring a Raman spectrum of an aromatic diol compound or alcohol obtained from the depolymerization; and a recovery unit for recovering the aromatic diol compound obtained from the depolymerization.

[0109] The depolymerization reaction of the polycarbonate-based resin in the presence of alcohol includes all of the above-described embodiments. The specific shape, material, and size of the reactor are not particularly limited, and various reactors that have been widely used in conventional polymer depolymerization reactions can be used without limitation.

[0110] The content of monitoring the Raman spectrum of the aromatic diol compound or alcohol inserted into the reactor and obtained from the depolymerization reaction includes all of the content described above in the embodiment.

[0111] The in-line analyzer may include a Raman analyzer. The Raman analyzer may be fabricated to withstand the reaction pressure and inserted into a reactor where the depolymerization reaction is performed to collect reaction information in real time. One end of the Raman analyzer may be in contact with the depolymerization reactants, and the other end may be connected to a computer to analyze the acquired Raman spectrum in real time. Specifically, the values ​​of Equation 1, Equation 2, and Equation 3 in the above embodiment may be analyzed by the computer.

[0112] The in-line analyzer may include a detector in contact with the reactants in the reactor. The in-line analyzer may further include a computer for analyzing the Raman spectrum measured by the in-line analyzer. One end of the in-line analyzer may be in contact with the reactants in the reactor, and the other end may be connected to a computer to analyze the acquired spectrum in real time.

[0113] The recovery of the aromatic diol compound obtained from the depolymerization reaction in the recovery unit includes all of the above-described embodiments. The specific shape, material, and size of the recovery unit are not particularly limited, and various recovery devices that have been widely used in conventional polycarbonate depolymerization reactions can be applied without limitation. However, for example, a distillation device, a washing device, a filtration device, a recrystallization device, etc. can be used as the recovery unit.

[0114] While specific examples of the apparatus for producing a monomer composition for synthesizing recycled plastics according to another embodiment of the present invention are not limited to these, an example illustrated in Figure 3 below may include a reactor 1 for depolymerizing a polycarbonate resin in the presence of alcohol, an in-line analyzer 2 inserted into the reactor for monitoring the Raman spectrum of the aromatic diol compound or alcohol obtained from the depolymerization, and a recovery unit 5 for recovering the aromatic diol compound obtained from the depolymerization. More specifically, the in-line analyzer may include a detection unit 3 in contact with the reactants in the reactor. The apparatus may further include a computer 4 for analyzing the Raman spectrum measured by the in-line analyzer.

[0115] 3. Monomer composition for synthesizing recycled plastics According to another embodiment of the present invention, there can be provided a monomer composition for synthesizing recycled plastics, comprising an aromatic diol compound obtained by the method for producing a monomer composition for synthesizing recycled plastics according to the one embodiment or the apparatus for producing a monomer composition for synthesizing recycled plastics according to the other embodiment.

[0116] That is, the monomer composition for synthesizing recycled plastics according to the other embodiment may be obtained by the method for producing the monomer composition for synthesizing recycled plastics according to the first embodiment. The content of the method for producing the monomer composition for synthesizing recycled plastics according to the first embodiment includes all of the content described above in the first embodiment.

[0117] In addition, the monomer composition for synthesizing recycled plastics of the other embodiment may be obtained by the apparatus for producing the monomer composition for synthesizing recycled plastics of the other embodiment. The content relating to the apparatus for producing the monomer composition for synthesizing recycled plastics of the other embodiment includes all of the content described above in the other embodiment.

[0118] Specific examples of the aromatic diol compound include bis(4-hydroxyphenyl)methane, bis(4-hydroxyphenyl)ether, bis(4-hydroxyphenyl)sulfone, bis(4-hydroxyphenyl)sulfoxide, bis(4-hydroxyphenyl)sulfide, bis(4-hydroxyphenyl)ketone, 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), 2,2-bis(4-hydroxyphenyl)butane, 1,1-bis(4-hydroxyphenyl)cyclohexane (bis Examples of the aromatic diol compound include 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, 2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane, 2,2-bis(4-hydroxy-3-bromophenyl)propane, 2,2-bis(4-hydroxy-3-chlorophenyl)propane, 2,2-bis(4-hydroxy-3-methylphenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, and mixtures of two or more thereof. Preferably, the aromatic diol compound in the monomer composition for synthesizing recycled plastics according to the embodiment may be 2,2-bis(4-hydroxyphenyl)propane (bisphenol A).

[0119] The aromatic diol compound is obtained by the method for producing a monomer composition for synthesizing recycled plastics according to one embodiment or the apparatus for producing a monomer composition for synthesizing recycled plastics according to another embodiment. That is, the aromatic diol compound is recovered from the polycarbonate resin used to recover the monomer composition for synthesizing recycled plastics. Therefore, when a new aromatic diol compound is added externally, separately from the one recovered from the polycarbonate resin, to produce the monomer composition for synthesizing recycled plastics according to another embodiment, it is not included in the scope of the aromatic diol compound of the present invention.

[0120] Specifically, the term "recovered from a polycarbonate-based resin" means that the polycarbonate-based resin is obtained by depolymerization of the polycarbonate-based resin. The depolymerization may be carried out under acidic, neutral, or basic conditions, and is particularly allowed to proceed under basic (alkaline) conditions. In particular, the depolymerization is preferably carried out in an ethanol solvent, as described below.

[0121] 4. Recycled plastic According to yet another embodiment of the present invention, there is provided a recycled plastic comprising a reaction product of the monomer composition for synthesizing recycled plastic according to the other embodiment and a comonomer.

[0122] The content relating to the monomer composition for synthesizing recycled plastics of the other embodiment includes all of the content described above in the other embodiment.

[0123] Examples of the recycled plastics are not particularly limited, and various plastics synthesized using an aromatic diol compound such as bisphenol A and a carbonate precursor such as dimethyl carbonate, diethyl carbonate, or ethyl methyl carbonate as a monomer can be used without limitation. A more specific example is a polycarbonate resin.

[0124] The term "polycarbonate-based resin" refers to any homopolymer or copolymer containing a polycarbonate repeating unit, and is a general term for reaction products obtained by the polymerization or copolymerization of monomers containing an aromatic diol compound and a carbonate precursor. A homopolymer can be synthesized by using only one type of carbonate repeating unit obtained using only one aromatic diol compound and one carbonate precursor. Alternatively, a copolymer can be synthesized by using one aromatic diol compound and two or more carbonate precursors, two or more aromatic diol compounds and one carbonate precursor, or one aromatic diol compound and one carbonate precursor plus one or more other diols to produce two or more carbonates. The homopolymer or copolymer can include low molecular weight compounds, oligomers, and polymers within a range of molecular weights.

[0125] More specifically, in the recycled plastics containing the reaction product of the monomer composition for recycled plastic synthesis and a comonomer according to the embodiment, the comonomer may be a carbonate precursor, such as phosgene, triphosgene, diphosgene, bromophosgene, dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dicyclohexyl carbonate, diphenyl carbonate, ditolyl carbonate, bis(chlorophenyl)carbonate, m-cresyl carbonate, dinaphthyl carbonate, bis(diphenyl)carbonate, or bishaloformates.

[0126] The reaction process of the monomer composition and comonomer for synthesizing recycled plastics to synthesize the polycarbonate-based resin is not particularly limited, and various conventionally known polycarbonate manufacturing methods can be applied without limitation.

[0127] However, as an example of the method for producing polycarbonate, a method for producing polycarbonate can be used that includes polymerizing a composition containing a monomer composition for synthesizing recycled plastics and a comonomer. In this case, the polymerization can be performed by interfacial polymerization, which can be performed at atmospheric pressure and low temperature, and allows for easy molecular weight control.

[0128] The polymerization temperature may be 0° C. to 40° C., and the reaction time may be 10 minutes to 5 hours. The pH during the reaction may be maintained at 9 or higher or 11 or higher.

[0129] The solvent that can be used in the polymerization is not particularly limited as long as it is a solvent that is used in the polymerization of polycarbonates in the art. For example, halogenated hydrocarbons such as methylene chloride and chlorobenzene can be used.

[0130] The polymerization can be carried out in the presence of an acid binder, and examples of the acid binder include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and amine compounds such as pyridine.

[0131] Furthermore, the polymerization can be carried out in the presence of a molecular weight regulator to control the molecular weight of the polycarbonate. The molecular weight regulator can be an alkylphenol having 1 to 20 carbon atoms, and specific examples include p-tert-butylphenol, p-cumylphenol, decylphenol, dodecylphenol, tetradecylphenol, hexadecylphenol, octadecylphenol, eicosylphenol, docosylphenol, or triacontylphenol. The molecular weight regulator can be added before, during, or after the initiation of polymerization. The molecular weight regulator can be used in an amount of 0.01 to 10 parts by weight, or 0.1 to 6 parts by weight, per 100 parts by weight of the aromatic diol compound, and the desired molecular weight can be obtained within this range.

[0132] In addition, to accelerate the polymerization reaction, a reaction accelerator such as a tertiary amine compound, a quaternary ammonium compound, or a quaternary phosphonium compound, such as triethylamine, tetra-n-butylammonium bromide, or tetra-n-butylphosphonium bromide, may be additionally used.

[0133] 5. Molded products According to yet another embodiment of the present invention, there is provided a molded product including the recycled plastic of the other embodiment. The content relating to the recycled plastic includes all of the content described above in the other embodiment.

[0134] The molded product may be obtained by applying the recycled plastic to various known plastic molding methods without limitation, and examples of the molding methods include injection molding, foam injection molding, blow molding, and extrusion molding.

[0135] The molded products are not particularly limited and may be applied to various molded products using plastics without limitation, such as automobile parts, electrical and electronic products, communication products, daily necessities, building materials, optical parts, exterior materials, etc.

[0136] In addition to the recycled plastic of the other embodiment, the molded article may further contain, as necessary, one or more additives selected from the group consisting of antioxidants, plasticizers, antistatic agents, nucleating agents, flame retardants, lubricants, impact modifiers, fluorescent brighteners, ultraviolet absorbers, pigments, and dyes.

[0137] An example of a method for manufacturing the molded product may include thoroughly mixing the recycled plastic of the other embodiment and an additive using a mixer, extruding the mixture in an extruder to form pellets, drying the pellets, and then injecting the pellets into an injection molding machine. [Effects of the Invention]

[0138] According to the present invention, there are provided a method and an apparatus for producing a monomer composition for synthesizing recycled plastics, which are capable of improving efficiency by optimizing reaction conditions through real-time monitoring of the process of recycling aromatic diol compounds by chemical decomposition of polycarbonate resins, and a monomer composition for synthesizing recycled plastics, recycled plastics, and molded articles using the same. [Brief explanation of the drawings]

[0139] [Figure 1] FIG. 1 shows Raman spectra obtained in Examples. [Figure 2] 1 is a diagram showing the integral ratio of aromatic diol compounds and the integral ratio of alcohols obtained in Example 1. FIG. [Figure 3] FIG. 1 is a schematic diagram of an apparatus for producing a monomer composition for synthesizing recycled plastics. DETAILED DESCRIPTION OF THE INVENTION

[0140] The present invention will be described in more detail in the following examples, but the following examples are merely illustrative of the present invention and are not intended to limit the scope of the present invention.

[0141] <Example: Production of recycled bisphenol A monomer composition> Example 1 (1. Decomposition step) 1 mol of waste polycarbonate (PC) was added to reactor 1 and dissolved in methylene chloride (MC), after which foreign matter was filtered out. Then, 11 mol of ethanol (EtOH), 0.2 mol of sodium hydroxide (NaOH), and an antioxidant were added, and the mixture was stirred at 60°C to allow the depolymerization reaction of PC to proceed.

[0142] During the depolymerization reaction of PC, an in-line analyzer 2, a Raman probe, was inserted into the reactor 1, and the viscosity of the polycarbonate (PC) was prevented from obstructing the detection unit 3 during stirring. After the start of the reaction, the Raman spectra were measured at regular intervals (approximately 3 minutes) for a total of 6 hours, and analyzed in real time by a program on the computer 4. The reaction was terminated at the optimum point (BPA / MC Raman integral ratio = 0.12).

[0143] (2. pH Adjustment) The product of the depolymerization reaction was cooled to 30° C. or less, and then adjusted to pH 8 by adding 10% hydrochloric acid (HCl) and water.

[0144] After (3. Layer separation), an aqueous layer and a methylene chloride (MC) layer were formed. The organic layer located at the bottom was recovered using a drain device at the bottom of the reactor, and the aqueous layer located at the top was discharged and discarded.

[0145] (4. Distillation) After that, the recovered methylene chloride (MC) layer was transferred to the recovery section 5, and the by-product diethyl carbonate (DEC) was separated and recovered by low-temperature distillation at a reduced pressure of 250 mbar, 20-30°C, and then at 30 mbar, 30°C.

[0146] After (5. Purification step - filtration), the residue from which diethyl carbonate (DEC) was removed was washed with methylene chloride (MC) in an amount twice the mass of the PC used at 20-30°C and then vacuum filtered.

[0147] (6-1. Additional purification step - redissolution step) Then, bisphenol A was redissolved in 16.6 mol of ethanol.

[0148] (6-2. Additional Purification Step-Adsorption Step) Then, lignite activated carbon was added as an adsorbent in a ratio of 30% by weight to the waste polycarbonate, and purified through an adsorption tower for 3 hours, and then the lignite activated carbon was removed by filtration.

[0149] (6-3. Additional Purification Step-Recrystallization Step) Then, water was added to recrystallize bisphenol A, and the resulting slurry was subjected to vacuum filtration at 20 to 30°C to recover bisphenol A (BPA) crystals.

[0150] (7. Drying step) After that, the mixture was vacuum dried in a convection oven at 40°C to prepare a recycled bisphenol A monomer composition from which recycled bisphenol A (BPA) was recovered.

[0151] Example 2 A recycled bisphenol A monomer composition was prepared in the same manner as in Example 1, except that (1. Decomposition step) in Example 1 was changed as follows.

[0152] (1. Decomposition step) 1 mol of waste polycarbonate (PC) was added to reactor 1 and dissolved in methylene chloride (MC), after which foreign matter was filtered out. Then, 11 mol of ethanol (EtOH), 0.2 mol of sodium hydroxide (NaOH), and an antioxidant were added, and the mixture was stirred at 80°C to allow the depolymerization reaction of PC to proceed.

[0153] During the depolymerization reaction of PC, an in-line analyzer 2, a Raman probe, was inserted into the reactor 1, and the viscosity of the polycarbonate (PC) was kept from obstructing the detection unit 3 during stirring. After the start of the reaction, the Raman spectra were measured at regular intervals (approximately 3 minutes) for a total of 6 hours, and analyzed in real time by a computer 4. The reaction was terminated at the optimum point (BPA / MC Raman integral ratio = 0.12).

[0154] <Experimental Example> The physical properties were measured by the following methods, and the results are shown in Tables 1 and 2 and Figs.

[0155] 1. Raman spectrum analysis results (1) Integral ratio of aromatic diol compounds In the above Example (1. Decomposition Step), the integral ratio of bisphenol A (BPA), an aromatic diol compound, was determined using an in-line Raman analyzer at regular time intervals (about 3 minutes) for a total of 6 hours after the start of the depolymerization reaction of PC. The results are shown in Table 1 and FIG. 2 for Example 1 and Table 2 for Example 2. Specifically, the integral ratio of the aromatic diol compound (BPA) was calculated using the BPA band (791.2 cm) as shown in the following Equation 1. -1 ~861.5cm -1 ) integral value of the MC band (663.4 cm -1 ~785.1cm -1 , and 234.8 cm -1 ~337.1cm -1 ) can be calculated by dividing it by the integral value of

[0156] [Formula 1] Integral ratio of aromatic diol compounds = {791.2 cm on the Raman spectrum -1 ~861.5cm -1 The integral value of the region / (663.4 cm on the Raman spectrum) -1 ~785.1cm -1 + 234.8 cm on the Raman spectrum -1 ~337.1cm -1 (Integral value of the domain) In the above formula 1, 791.2 cm -1 ~861.5cm -1 The region of the spectrum is due to bisphenol A (BPA), and is at 663.4 cm on the Raman spectrum. -1 ~785.1cm -1 , and 234.8 cm -1 ~337.1cm -1 The region is the spectrum obtained by methylene chloride (MC).

[0157] The Raman analysis was performed using MarqMetrix's All-in-one device and Ball Probe to measure the spectrum inside the reactor in real time under the condition of an Excitation Laser (785 nm, 400 MW), and baseline correction was performed linearly in the regions of each component of MC and BPA.

[0158] (2) Integral ratio of alcohol In the example (1. Decomposition step), the integral ratio of alcohol (ethanol (EtOH)) was measured at regular time intervals (about 3 minutes) for a total of 6 hours after the start of the depolymerization reaction of PC using an in-line Raman analyzer. The results are shown in Table 1 and Figure 2 for Example 1. Specifically, the integral ratio of alcohol (EtOH) was calculated using the EtOH band (849.7 cm) as shown in the following Equation 2. -1 ~910cm -1 ) integral value of the MC band (663.4 cm -1 ~785.1cm -1 , and 234.8 cm -1 ~337.1cm -1 ) can be calculated by dividing it by the integral value of

[0159] [Formula 2] Integral ratio of alcohol = {849.7 cm on the Raman spectrum -1 ~910cm -1 The integral value of the region / (663.4 cm on the Raman spectrum) -1 ~785.1cm -1 + 234.8 cm on the Raman spectrum -1 ~337.1cm -1 (Integral value of the domain) In the above formula 2, 849.7 cm -1 ~910cm -1 The region of the spectrum is due to ethanol (EtOH), and the region of the spectrum is 663.4 cm -1 ~785.1cm -1 , and 234.8 cm -1 ~337.1cm -1The region is the spectrum obtained by methylene chloride (MC).

[0160] The Raman analysis was performed using a MarqMetrix All-in-one device and a Ball Probe to measure the spectrum inside the reactor in real time under the condition of an Excitation Laser (785 nm, 400 MW), and baseline correction was performed linearly in the regions of each component, EtOH and BPA.

[0161] 2. BPA yield In the above Example (1. Decomposition step), the weight of bisphenol A (BPA) produced during the depolymerization reaction was measured by HPLC at regular time intervals (about 3 minutes) for a total of 6 hours after the start of the depolymerization reaction of PC. The weight of BPA produced when the polycarbonate used in the reaction was 100% decomposed was measured, and the BPA yield was calculated using the following Equation 4.

[0162] [Formula 4] Yield (%) = (W1 / W0) x 100 In the above formula 4, W0 is the mass of BPA obtained at 100% decomposition, and W1 is the mass of BPA actually obtained. Specifically, when approximately 100 g of polycarbonate is decomposed, the mass of BPA theoretically obtained at 100% decomposition is 89 g. If the mass of BPA actually obtained is 80 g, the yield is (80 / 89) × 100 = 90%.

[0163] [Table 1]

[0164] [Table 2] [Explanation of symbols]

[0165] 1: Reactor 2: In-line analyzer 3: Detection unit 4: Computer 5: Recovery department

Claims

1. depolymerizing a polycarbonate resin in the presence of alcohol; monitoring a Raman spectrum of the aromatic diol compound or alcohol obtained from the depolymerization reaction in a reactor where the depolymerization reaction is performed; and recovering the aromatic diol compound.

2. The step of monitoring a Raman spectrum of the aromatic diol compound or alcohol obtained from the depolymerization reaction in a reactor where the depolymerization reaction is performed includes:

2. The method for producing a monomer composition for synthesizing recycled plastics according to claim 1, wherein the method is carried out using a Raman spectrometer inserted in a reactor.

3. The step of monitoring a Raman spectrum of the aromatic diol compound or alcohol obtained from the depolymerization reaction in a reactor where the depolymerization reaction is performed includes:

2. The method for producing a monomer composition for synthesizing recycled plastics according to claim 1, comprising measuring an integral ratio of an aromatic diol compound according to the following Equation 1: [Formula 1] Integral ratio of aromatic diol compound = {791.2 cm on the Raman spectrum -1 ~861.5cm -1 The integral value of the region / (663.4 cm on the Raman spectrum -1 ~785.1cm -1 + 234.8 cm on the Raman spectrum -1 ~337.1cm -1 (integral value of the region) In the above formula 1, 791.2 cm on the Raman spectrum -1 ~861.5cm -1 The region of the spectrum is due to aromatic diol compounds, 663.4 cm on the Raman spectrum -1 ~785.1cm -1 , and 234.8 cm -1 ~337.1cm -1 The region is the spectrum due to the reaction solvent.

4. 4. The method of claim 3, wherein the depolymerization reaction is terminated when the integral ratio of the aromatic diol compound according to Equation 1 is 0.115 to 0.

125.

5. The step of monitoring a Raman spectrum of the aromatic diol compound or alcohol obtained from the depolymerization reaction in a reactor where the depolymerization reaction is performed includes:

2. The method for producing a monomer composition for synthesizing recycled plastics according to claim 1, comprising measuring an integral ratio of alcohol according to the following Equation 2: [Formula 2] Alcohol integral ratio = {849.7 cm on the Raman spectrum -1 ~910cm -1 The integral value of the region / (663.4 cm on the Raman spectrum -1 ~785.1cm -1 + 234.8 cm on the Raman spectrum -1 ~337.1cm -1 (integral value of the region) In the above formula 2, 849.7 cm on the Raman spectrum -1 ~910cm -1 The region is the spectrum of alcohol, 663.4 cm on the Raman spectrum -1 ~785.1cm -1 , and 234.8 cm -1 ~337.1cm -1 The region is the spectrum due to the reaction solvent.

6. 6. The method for producing a monomer composition for synthesizing recycled plastics according to claim 5, wherein the depolymerization reaction is terminated when the integral ratio of the alcohol according to Equation 2 is 0.09 to 0.

1.

7. 2. The method for producing a monomer composition for synthesizing recycled plastics according to claim 1, wherein the aromatic diol compound is bisphenol A.

8. 2. The method for producing a monomer composition for synthesizing recycled plastics according to claim 1, wherein the alcohol is ethanol.

9. The step of monitoring a Raman spectrum of the aromatic diol compound or alcohol obtained from the depolymerization reaction in a reactor where the depolymerization reaction is performed includes:

2. The method for producing a monomer composition for synthesizing recycled plastics according to claim 1, further comprising monitoring a Raman spectrum of impurities derived from the aromatic diol compound produced in the depolymerization reaction.

10. The step of monitoring the Raman spectrum of impurities derived from the aromatic diol compound produced in the depolymerization reaction includes:

10. The method for producing a monomer composition for synthesizing recycled plastics according to claim 9, comprising measuring an integral ratio of impurities derived from aromatic diol compounds according to the following Equation 3: [Formula 3] Integral ratio of impurities derived from aromatic diol compounds = {800 cm on the Raman spectrum -1 ~850cm -1 The integral value of the region / (663.4 cm on the Raman spectrum -1 ~785.1cm -1 + 234.8 cm on the Raman spectrum -1 ~337.1cm -1 (integral value of the region) In the above formula 3, 800 cm on the Raman spectrum -1 ~850cm -1 The region of is a spectrum due to impurities derived from aromatic diol compounds, 663.4 cm on the Raman spectrum -1 ~785.1cm -1 , and 234.8 cm -1 ~337.1cm -1 The region is the spectrum due to the reaction solvent.

11. The method for producing a monomer composition for synthesizing recycled plastics according to claim 10, wherein the depolymerization reaction is terminated if the integral ratio of impurities derived from the aromatic diol compound according to Equation 3 exceeds 0.

12.

12. The step of monitoring a Raman spectrum of the aromatic diol compound or alcohol obtained from the depolymerization reaction in a reactor where the depolymerization reaction is performed includes:

2. The method for producing a monomer composition for synthesizing recycled plastics according to claim 1, wherein the process is repeated at intervals of 5 minutes or less.

13. a reactor for depolymerizing a polycarbonate resin in the presence of alcohol; an in-line analyzer inserted into the reactor to monitor the Raman spectrum of the aromatic diol compound or alcohol obtained from the depolymerization reaction; a recovery section for recovering the aromatic diol compound obtained from the depolymerization reaction.

14. The in-line analyzer 14. The apparatus for producing a monomer composition for synthesizing recycled plastics according to claim 13, comprising a Raman measuring instrument.

15. The apparatus for producing a monomer composition for synthesizing recycled plastics according to claim 13, further comprising a computer for analyzing the Raman spectrum measured by the in-line analyzer.

16. The apparatus for producing a monomer composition for synthesizing recycled plastics according to claim 13, wherein the in-line analyzer includes a detection unit in contact with the reactants in the reactor.

17. A monomer composition for synthesizing recycled plastics, comprising an aromatic diol compound obtained by the method for producing a monomer composition for synthesizing recycled plastics according to claim 1 or the apparatus for producing a monomer composition for synthesizing recycled plastics according to claim 13.

18. A recycled plastic comprising the reaction product of the recycled plastic synthesis monomer composition of claim 17 and a comonomer.

19. A molded article comprising the recycled plastic of claim 18.

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